


Undertale Headcanons

by PrinceOfSleeping



Category: Undertale (Video Game)
Genre: Alternate Universe - Bittybones (Undertale), Alternate Universe - Dreamtale (Undertale), Alternate Universe - Horrortale (Undertale), Alternate Universe - Underfell (Undertale), Alternate Universe - Underlust (Undertale), Alternate Universe - Underswap (Undertale), Headcanon, Multi, Other AUs not listed
Language: English
Status: In-Progress
Published: 2019-11-08
Updated: 2020-05-17
Packaged: 2021-01-25 11:47:49
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 6
Words: 1,457
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21355768
Author URL: https://archiveofourown.org/users/PrinceOfSleeping/pseuds/PrinceOfSleeping
Summary: This is a big thing on tumblr, but I thought I'd try it out here? So go ahead, fill my comments! You should know what to do. ;)
Relationships: Grillby/Sans (Undertale), Mettaton/Papyrus (Undertale), Other Relationship Tags to Be Added
Comments: 22
Kudos: 25





	1. The Basic Idea

If you're somebody who frequents Tumblr, you know the drill. But if you don't, here's the basics. You ask how a character would react to something and I tell ya how I think they would. Or just random little trivia about their life. That sorta deal. 

So I guess there should be some rules?  
\- 5 characters max per ask (But you can just ask it again with different characters in another ask, don't worry)  
\- Ships are allowed, but please be respectful if I decline (Which I most likely won't, me being a multishipper lol)  
\- Nsfw is allowed  
\- All AU's allowed  
\- Now allowing all characters!  
\- X reader is allowed, but no oc's

Also, I may add match ups if anybody is interested. I think that covers it? Yeah. Anyway, my awkwardness aside, I hope we can all have fun! If this wasn't clear enough on what I'm doing, then look at some of the chapters in this work. <3


	2. Random Underlust Sans Headcanons

**Summary for the Chapter:**

> Just some random headcanons

Random Underlust Sans Headcanons  
▪Unlike what some people think, he understands and respects people's boundaries and consent.  
▪He's still a big flirt tho.  
▪If you aren't down to fuck, he's still game to chill out and stuff.  
▪Secretly loves romcoms. Don't ask me why, he just does.  
▪Not a complete romantic like his bro, but he'll give his partner a flower or chocolate occasionally.  
▪He's thinner than other Sans's, most likely from pole dancing.   
▪Oh yeah. He's like, a pro at pole dancing.   
▪Gives good clothing advice. Take him shopping with you  
▪His drink is Zesty Italian Salad Dressing and nobody can tell me otherwise.


	3. Random Bitty Headcanons

**Summary for the Chapter:**

> Just my personal headcanons for bitties.

Sansy Bitties  
▪Super lazy beans. They love to snuggle up with their caretaker and/or other bitties.  
▪Good listeners if you just need to rant.  
▪Absolute nerds! Give your Sansy a book about astrology and he'll cherish it forever. 

Papy Bitties  
▪Super friendly! Great at making even the most timid people feel safe.  
▪Love to help out with chores of any kind! Cooking is their absolute favorite!  
▪They really care about their loved ones. They will do everything they can to make sure you know this.  
▪ If you're sad one day you may find a tiny gift on your pillow when you wake up the next day.

Baby Blue Bitties  
▪These lil sweeties adore action films! Let them snuggle up with you and marathon stuff like Karate Kid!  
▪Your little knight! They won't hesitate to come to your rescue! Whether it be telling someone they have done/said something wrong or giving you a bandaid, these beans live to serve n protecc.  
▪As much as they adore tacos, Baby Blues really enjoy fruits, nuts, or any other type of healthy snack. Be sure to carry some with you.

Lil Bro Bitties  
▪The most chill bitties. Just wanna nap all day? Here's your new nap buddy! Wanna stay inside n binge a show? They'll cozy up with you for as long as ya like!  
▪Actually really good at giving advice. Not so much on taking it though.  
▪A fan of sweets. Mostly honey and honey flavored things, but they also like chocolate oranges.

Edgy Bitties  
▪Not as dangerous or prone to destroy property as they're made out to be. The only reason an Edgy would behave this way would be if they felt threatened or are troubled bitties from abuse cases.  
▪They will growl, bite, or scratch people they think are a threat to them or their loved ones. They are very protective. They're also known to leer at strangers while riding on your shoulder, or in a pocket/hood.  
▪Under all that 'Edge' is a genuinely sweet bitty who desperately wants to keep you safe. They love affection but can sometimes be too shy to ask or show it. Basically grumpy little teddybears.  
▪They care just as much about any other bitties they may live with as they do their caretaker. They may huff and pout all they want, but we all know they are very happy to be loved.

Boss Bitties  
▪Hope you like waking up early. These little soldiers love having schedules. They also make sure you do your chores and take good care of yourself.  
▪They'll happily help you to rearrange your things. They make sure to keep track of things and know where everything is. You know you can count on them if you misplace something.  
▪They love watching war films and documentaries. Also movies that involve kingdoms. 

Cherry Bitties  
▪Nervous and anxious beans, but not to the point of being incapable of taking care of themselves like some people think.  
▪They stutter and sometimes have a hard time getting across what they're trying to say. Please be patient with them, they are trying their hardest.  
▪They really like having necklaces, as it gives them something to fiddle with when they don't know what to do with their hands. 

Softybones Bitties  
▪Even lazier than a Sansy or Lil Bro. They are also narcoleptic, and often end up falling asleep in weird places.  
▪They space out alot and may ask you to repeat what you said a second or third time.  
▪Really like marshmallows for some reason. Perhaps because they remind them of pillows?


	4. Random Nightmare Sans Headcanons

**Summary for the Chapter:**

> Some random Nightmare headcanons

Nightmare Sans Headcanons  
▪When he's not out feeding off negativity, then he's usually reading books. He has accumulated enough books to have a library at this point. His favorite genre is horror, but he also enjoys a good murder mystery.  
▪He cannot enter aus that are filled with positivity, as in every single entity feeling positive emotions, or teleport to somebody feeling positively.  
▪Positive auras don't hurt him, they're more of an annoyance.  
▪The black goop that took over him has replaced his bones, granting him the ability to reshape his form after taking damage. This same ability could be used to shapeshift, but he feels more familiar with his skeletal form.  
▪He can become a goop puddle and slip under doors and through cracks in walls. He is the ultimate Sleep Paralysis Demon™.  
▪Depending on the multiverse, he either has a castle or his own 'anti-void' of sorts. He's gotta put all his books somewhere right?  
▪Corrupted!Nightmare is a different person than Uncorruptedl!Nightmare. Goopy lad has similarities with the former version of himself, but he is not the same person. Which makes you wonder why he refers to Dream as his brother. Perhaps to get a negative response?  
▪The goop making up his form has a rubbery texture but turns sticky when being used in battle or to create his goop portals.  
▪He frequently visits negative aus such as Horrortale or Dusttale to feed off of. Just standing in the shadows like a creep.


	5. Lust Sans Bitty Headcanons

**Summary for the Chapter:**

> Here's a request I shoulda done sooner, but life was kinda in the way. These were originally supposed to be of the adoptions themselves, but I couldn't think of how exactly I wanted them to happen. I hope thats alright!

Regular Lust Bitty  
▪These lovelies are big fashionistas and adore having lots of clothing. Whether bought or handmade, as long as it's cute it'll be worn.  
▪They tend to prefer sleeping with other beings, whether it be their caretaker or other bitties.  
▪Often found sunbathing in windowsills or relaxing in piles of pillows.  
▪They secretly love romcoms, even if they tend to make snarky comments or nitpick them.  
▪Pretty fond of berries and chocolates, so be sure to keep those in stock  


Lamia Lust Bitty  
▪This lovely noodle is often found curled around your arm or laying across your shoulders.  
▪A big fan of cuddles and may even give you smooches if you're comfortable with them doing so.  
▪Asks for clothes and jewelry a lot. You can also ask them for clothing advice, they're very trendy.  
▪These cuddle noodles need to bathe regularly in order to keep shiny. Oh yeah, they have some of the most shiniest scales of all the lamias.  
▪They prefer being held and carried as to not dirty their beautiful scales.  



	6. Underlust Sansby and Papyton headcanons

**Summary for the Chapter:**

> Part 1/3 of a request! Thought I'd put both ships in the same chapter since it's the same au. Hope these turned out alright!
> 
> Mentions of NSFW kinda? Idk it's underlust lmao.

Underlust Sansby  
▪Sans works at Grillby's for free food. Which is just salad dressing usually.  
▪Sans will sometimes pester Grillby into joining him up on stage. The patrons always go crazy for the duo.  
▪Grillby is often the one planning dates for the two.  
▪Many pickup line contests between the two. Grilbz is a bit more savy, whilst Sans starts off sweet and ends up super raunchy.  
▪They don't fuck as much as you'd think. I mean don't get me wrong, they DO fuck, but they are also both sick of how sexual everything is all the time.  


Underlust Papyton  
▪These two are always in contact, whether by hanging out or through text/calling.  
▪Papyrus is always sure to be gentle with Mettaton and give him his space when he gets overwhelmed.  
▪Mettaton has ptsd from his attack, but he always has Paps there ready to comfort him.  
▪Constant movie nights. Paps likes watching Mettaton's stuff, which Metta finds flattering (and a tad embarrassing).  
▪Honestly, they're just super wholesome and help eachother cope with stuff.  



End file.
